Process for calcining ores



W. H. CRBOULD. PROCESS FOR CALCNING CRES. APPLICATION HLED OCT. 7| 19191 1,358,293. Patented Nov. 9, 1920.

WILLIAM H. CORBOULD, 0F SELW'YN, QUEENSLAND, AUSTRALIA.

:PROCESS FOB. CALCINING GRES.

Specification of Letters Patent. y

Patented Nov. 9, 1920.

i Application letl October 7, 1919. Serial No. 329,026.

To all 'whom t may concern.'

Be it known that I, VYLLIAM HENRY CoRnoULD, a. subject of Great Britain, residing at Selwyn, in the State of Queensland, Commonwealth of Australia, have invented certain new and useful improvements in Processes for Calcininp; Orcs, of which the following; is a specification.

This invention relates to an improved process for calcining` ores and their gangue and. more especially toores of copper and their gangue, and apparatus therefor, and has for its object the providing ot process and means whereby greater efficiency and increased economyV arc obtained than has been the practice heretofore.

I have'found that when finely ground ore products, with special reference to ores of copper and their gangue, are subjected to heat and air pressure, the chemical and catalytical actions are perfect and rapid.

ln this invention I make use of this discovery by subjecting the contents of the roasting furnace herein described to a plenum of air and to an exhausted atxnosphere alternately.

in the accompanying sheet of drawing a longitudinal section ispshown of apparatus of novel construction for the carrying out of the invention.

i is the tire box. and 2 the furnace bars, 3 the briclrwork lining of the pipe 4 through which the heated grases of combustion iow from the tire box 'l to the roastcr. through the annular chamber 5 and the inclosina annular passage 6. The outer lwall 7 of the annular passage (i constitutesthe surface from which the heat is radiated to heat the contents of the roasting furnace. From this chamber (i the yases flow th rousrh apassag'enot shown-to the chimney tlue orlstack 8 and so on to the outer air. or elsewhere when required. to he used for further hcatinelr purposes. When the temperature of calcining does not exceed S00 to 900 degrees Fahr. the heat radiating tubes may be constructed of cast iron. But when the required heat exceeds the above mentioned temperaturesait is necessary to use materials of greater heat resistintrqualities.` ln such case a heatresistin;imetal alloy isemplo'vcd. or the tubes are built in situ of special dovetailed tircbriek, chrome brick, or crushed chrome and silicate of soda mixture suitably reinforced. 9 is the shell of the roasting chamber which is constructedof sufficienty strength to withstand the requisite air and gas pressure, l0 the riding rings thereof, supported upon rollers 11. 12 is the driving wheel, 13 the driving worm, and 14: the pulley to which power is applied for operating the worm and wheel. The shell 9 and the dished ends oi the roasting chamber 15 are suitably covered internally with aV lagging 16 composed either of slag, reinforced sand and cement mixture. irebricl'r, chrome or magnesite brick, or a mixture of pulverized chrome and silicate of soda, and the heat radiating tube 7, and its stays 17 are similarly lagged. These stays 17 are secured each at one end tothe shell plate 9 of the roasting furnace, and each at the other end, to the shell plate 7 of the heat radiator.

In the dished ends 18 and 18a are formed and positioned a plurality of filter boxes 19 through which compressed air-heated or otherwiseis periodically forced into the roasting chamber to form a plenum, and, through which are periodically withdrawn air and gases from the ,roasting chamber, to form a partial vacuum therein.

These filter boxes 19 are designed to effeet an even distribution of the enteringr compressed air. and. further to prevent the carrying' over of solid impurities by the exhaustine, air or gases. Depending' upon the class of oresundergoinfr treatment these objects are obtained by the use of such filtering media as asbestos cloth, special metal tilter cloth. or porous refractory material through which the air and vapors are caused to pass.

Compressed air is supplied from an air compressor and the ,erases \vitlulra\vn-`by the action of the air exhauster or fan--from the roasing furnace throuo'h the filter boxes 19. positioned on the dished end 15 ofthe furnace throueh the passages 20 and pipe Q1 and connections are established 'between such supply pipes bv the pipes QQ shown in dotted lines embedded in the leaning it* of the roasting furnae. 23 are their controllino.` check valves,

The pipe 21 is formed axially on the dished end 18 of the roasting furnace and the pipes or passages 2O are led into it. The 'free end of this pipe Q1 is housed within a gland and stutiin'gr box 24 to obviate air Vand `eas leakage and at the Vsame time to permit of free rotation therein. From the y stutline box 24 is led a pipe Q5 carryingtwo branches, one. QG. being: carried to an air exhauster-such as a. centrifugal fan, or such like mechanism,not shown in the draw-V ing-and the other branch 27, `to` an air" compressor-ln'ot shown? in the drawings;Y

Upon each of these branches is positioned a valve 28 and 29 respectively, the operative levers of which are mechanically coupled together by the'rod 30 which causesthem to move in unison. s Ihesevalvespmechanically coupled together as described are jointly operatedlby Corliss-valve gear mechaf nism 81.

This gear is'vjactuated, either an independent. motor,` or I such like contriva'nc'e, o1'k by mechanism operated by the rotation of the roasting furnace, as shown in the drawings. In this latter case the pulleys 32 in frictional contact with onev of .the rotating riding rings 10 actuates thefshaft 3 3, and.l

through it the bevel wheels 34 and the gear 31.

Safetyf'valves-Mnot shown-#are positioned at lvarious points ona line oli-the circumference of the barrel of the furnace and are operable when riding free of the guard 35. Vbut closed and inoperable when in contact i with such guard to obviatev leakage of the containedY ores when the valves are inverted;l 36 are the ore bins. 37 arethechargrng gates,i38 sliding collars thereon to connect' the discharge end AofV the latter ywith"4 the roasting furnace. charginggates 39j.V 40 is .the pit vinto which calcined ores fromthe kfurnace are discharged through Athe gates'39 when such are inverted over-the lpiti() to` discharge, and from whichA they are Vremoved by a conveyer'orsuchlike appliance. l1 are piped connections mounted upon the dished end 18of the roasting furnace to, provide means for blowing out the dust, soot, fand such like accumulations "fromthe radiator heating tubes. 42 are the pyrometer and testing connections.` s Y y In operation finely ground ores, together with their gangue are charged fromV the bins 36 into the roasting furnace, andwhen so charged the furnace is revolved yat a speed of about one-half Ito. one revolution` per minute; In exceptional cases, however, a Greater or less speedV may be employed;

he heated gases of combustion'pass from the fire box 1 through the tube 4 and traverse the passages 5 and 6, provided for them in the heat radiator, finally escaping as described, by means of the passage-'not shown-to the chimney flue or stack 8V.

The heat required for the carrying out of VVthe roasting operation is obtained by radiation, and owing to the construction and position of the radiator--within the roasting furnace-theheat so supplied is evenly distributed through the contents of the chamber 15 and so insures a uniform roast of the contents. v o y Y The air exhauster valve 28 and the lair compression valve 29 benglcoupled vto 4one another are, in consequence, operated simul- 4taiie'ously by the Corliss gear 31, and they are so' arranged that by the movement of the gear 31 onel valve is fully 'opened while the other one is fully closed, and vice versa; thus when the air compressor` is delivering compressed air to the roaster furnace through the valve 29 the Aair exhauster or fan is rendered inoperative by the ,closing of the valve 28 and so when thevalve'28 is opened l the'walve 29'is closed.` The speed* of rotationA of theroaste'r furnace, or other power driveV controlling the Corlissge'ar 31 regu lates the periodicity of these air operations.

This regulation of periodicity is necessary in the treatment of various classes'of ore as for instance in thecase' ofV a sulfidl ore, a gas rich in SO2 may be obtained or a gas lower in SOzmay be drawn offz by thesimple adj-ustment of the periodicity of operations'of the valves, or, by the regulating of the amount of their opening. A Y

Upon the opening of the valve 29 the compressed air from the compressor passes through the pipes 25 and 21 to the'passages 20 fromwhence a portion of the air finds its way into the roaster furnaceV chamber 15 through the filtering medium of the lter vboxesv'19 positioned inthe dished end 184 while the remainder flowsthrough the check lair non-return v'alve`23l and their pipes 22 to corresponding filter boxes l19 positioned in the dished end 18a,through which it is admitted `to the roaster furnace. ThusV cornpressed air is simultaneously admitted through a plurality of points to both ends of the furnace, thereby Vsecuring therein an equitable air: distribution throughout;

In Ithe reduction of certain'classes of ores and their ganguesit is found" advantageous to introduce chlorin gas underpressure, with or without compressed air. In this case the chlorin gas,- is introduced into'the roasting chamber through the plurality of points'as. above described and its supply is caused to alternate with a 4depletedatmosphere' as set out.` Y

Upon the closingof the valve 29 and the operating -of thevalve 28,the air exhaust fan` tary furnace, it is obvious that it' equally applicable to stationary furnaces.

Iclaimz Y 1. A process oflcalcining. ores ofcopper and their gangue consisting in subjecting the finely pulverized material to heat in a roasting furnace, While treating such product, alternately to the action of air under a pressure substantially above atmospheric and to a substantial partial vacuum, during such operation.

2. A process for the purposes specified consisting in roasting the finely ground ores of copper and their gangue by the application of heat in a furnace, periodically admitting compressed gas containing an ingredient capable of reacting with the said ore until a pressure substantially above atmospheric is produced, and periodically partially exhausting the contained gas and air from such furnace, to alternately produce a plenum and a partial vacuum therein, during such operation.

3. A process for the purposes specified consisting in roasting the finely ground ores of copper and their gangue by the application of heat in a furnace, periodically admitting compressed air and free oxygen to the said furnace, and periodically partially exhausting the contained gases therefrom to alternately produce a substantial plenum and a substantial partial vacuum therein during such process.

4:. In a process for the purposes specified and as set out in claim 1, the application of air and chlorin gas under pressure to the material undergoing treatment in the roasting chamber, and the Withdrawal of the products of combustion therefrom, for the purpose of alternately creating a substantial superatmospheric and substantial subatmospherio pressure, Within the said chamber during the roasting operation.

In testimony whereof I affix my signature in the presence of two Witnesses.

W. H. coRBoULD.

Witnesses:

H. N. YOUNG, E. M. CU'romsoN. 

